Compact HII regions toward Methanol Maser traced sources of Massive Star Formation. Adam Avison (UK ARC, JBCA) Gary Fuller + MMB Collaboration. Overview. HII Regions in sites of MSF The MMB Survey MMB Continuum sources characterisitcs Size differences as evolutionary indication Conclusion.
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Compact HII regions toward Methanol Maser traced sources of Massive Star Formation
Adam Avison (UK ARC, JBCA)
Gary Fuller + MMB Collaboration
Values from Kurtz 2002.
The obvious question to initially ask about these sources is are the Masers and HII regions associated?
Naively: “Some but not all”
1’’ @ 5kpc = 0.02pc
1000” @ 5kpc = 24pc
Sources with <10” separations from masers distance used are from (Green & McClure-Griffiths 2011 in prep).
Remaining sources used the near/far kinematic distances (Green 2008).
We used a couple of techniques to try and overcome this.
A simplistic emission measure was calculated for each source:
Which was then used to further characterize sources.
From the Evolutionary time lines of e.g. Breen et al. 2010 one would expect HII regions associated with masers to be smaller in size than those with greater maser/continuum separation.
This effect has been seen by e.g. Walsh et al. 1998 & Ellingsen et al. 2005.
Breen et al. 2010
Compared integrated-to-peak flux ratio for same split:
Things I haven’t said…